the cleaner wrasse
Cleaner wrasse not only have different cleaning techniques for different species they will recognise individual clients and clean them differently. As such fish will always go to the same cleaner station when they have too many parasites (every 4-6 days). Although cleaner wrasse eat parasites, the truth is they like the taste of fish mucous better (something the fish does not want the cleaner fish to eat) and sometimes they will give in to temptation and eat too much mucous. When they do this, the fish leaves and will then start going to a different cleaning station (just like what you would do after getting a bad haircut).